There is a national interest in the discovery of alternative sources of fuels and chemicals that are not derived from petroleum resources. As the public discussion concerning the availability of petroleum resources and the need for alternative sources continues to grow, it is anticipated that future government mandates will require transportation fuels to include, at least in part, hydrocarbons derived from sources besides petroleum. As such, there is a need to develop alternative sources for hydrocarbons useful for producing fuels and chemicals.
One possible alternative source of hydrocarbons for producing fuels and chemicals is the natural carbon found in plants and animals, such as for example, in the form of carbohydrates. These so-called “natural” carbon resources (or renewable hydrocarbons) are widely available, and remain a target alternative source for the production of hydrocarbons. For example, it is known that carbohydrates and other sugar-based feedstocks can be used to produce ethanol, which has been used in gasohol and other energy applications. However, the use of ethanol in transportation fuels has not proven to be cost effective and may not be achievable on a scale significant to current fuel requirements.
Carbohydrates, however, can also be used to produce fuel range hydrocarbons. Although some upgrading technology has been developed to turn biologically derived materials into useful fuel and chemical feedstocks. Unfortunately, many carbohydrates (e.g., starches) are undesirable as feedstocks due to the costs associated with converting them to a usable form. In addition, many carbohydrates are known to be “difficult” to convert due to their chemical structure, the hydrocarbon product produced is undesirable, or the conversion process results in relatively low yields of desirable products. Among the compounds that are difficult to convert include compounds with low effective hydrogen to carbon ratios like oxygenates, including carbohydrates such as starches, sugars, carboxylic acids and anhydrides, lower glycols, glycerin and other polyols, ethers, esters and short chain aldehydes.
Chen, et al. U.S. Pat. No. 4,503,278, teaches a process for the conversion of carbohydrates such as starch, cellulose and sugar into hydrocarbon products of increased carbon content. Chen, et al. U.S. Pat. No. 4,690,903, uses an ethanol fermentation process in which an aqueous solution of fermentable sugar is converted by an ethanol-producing microorganism such as a yeast to a dilute aqueous solution of ethanol with the ethanol being present in the solution at a concentration which does not exceed a predetermined maximum level. McAuliffe, et al. U.S. Pat. No. 5,336,819, teaches the conversion of cellulose to hydrocarbon fuel, particularly fuel oil can be carried out using a polycyclic hydrogen donor substance. Jelks, EP0366138, teaches a process for manufacturing fuel from lingo-cellulose material.
Efforts to convert difficult carbohydrate materials to hydrocarbons have focused on methods for increasing the effective hydrogen to carbon ratio of the reactants, including converting oxygenates in the presence of hydrogen, steam, or other reactants, and by employing various catalysts. However, these processes are often complex and are costly, and the reaction products produced as a result of these processes are oftentimes undesirable, result in low weight percentages, or often result in an increase in undesirable byproducts such as the production of carbon monoxide, carbon dioxide and worse yet difficult to process coke byproducts.
As such, development of an improved process for converting carbohydrates, including “difficult” to convert starches as mentioned above, to hydrocarbon, would be a significant contribution to the arts. In addition, development of a process for converting carbohydrates to hydrocarbons which yields significant quantities of desirable hydrocarbon products such as aromatics and olefins would be a significant contribution to the art.